There is conventionally known a linear motion guide bearing of a linear motion guide unit in which more than one row of rolling elements is disposed in only one load-carrying race. For instance, Japanese Patent No. 3 219 170 discloses a linear motion guide bearing in which rolling elements are arranged in a plural rows in a common or single load-carrying race for a purpose of keeping occurrence of any skew and/or tiny or minute vibration under control. With the linear motion guide bearing constructed as stated just earlier, bearing recesses of bearing body have races along which rollers circulate in two rows to allow a shaft and the bearing body to make linear motion each other. The rollers lying in two rows are arranged to be out of each other every row by a radius of the roller to allow the rollers to move independently each other.
Moreover, another motion guide device has been known in which no skew occurs even with any inclination error or lopsided load on the mounting surface. For instance, Japanese Laid-Open Patent Application No. 2011-112 069 discloses a linear motion guide device of roller type in which the rollers are disposed in a plurality of recirculation circuits and held by means of retainers made of synthetic resin. The prior linear motion guide unit is composed of a track member, a moving member having a plurality of load-roller rolling surfaces facing a plurality of roller rolling surfaces, a plurality of non-load return passages extending in parallel with the plurality of load-roller rolling surfaces and a plurality of turnaround passages connecting the load-roller rolling surfaces with the non-load return passages to form a plurality of roller recirculation circuits through which the rollers are allowed to roll in an endless manner. Of the plurality of roller recirculation circuits, at least one roller recirculation circuit has a plurality of rollers lying in more than two rows. Upon movement of the moving member relative to the track member in the lengthwise direction of the track member, the rollers lying in more than two rows roll through between the roller rolling surfaces on the track member and the load-roller rolling surfaces on the moving member to move along the roller recirculation circuits.
Meanwhile, the first prior linear motion guide bearing cited above has a problem in which the rollers would suffer frictional resistance that is encountered while the rollers adjoining in tandem axially of them turn on their axes with their axial ends sliding over each other. The second prior linear motion guide device, moreover, has a serious issue that the retainer to hold the more than two rows of rollers would become inevitably sophisticated in construction and a large scale in the overall construction as well as needs several more chores for the production thereof.